Part of vmc.contrib.louie.saferef View In Hierarchy
'Safe' and reusable weak references to instance methods. BoundMethodWeakref objects provide a mechanism for referencing a bound method without requiring that the method object itself (which is normally a transient object) is kept alive. Instead, the BoundMethodWeakref object keeps weak references to both the object and the function which together define the instance method. Attributes: - ``key``: The identity key for the reference, calculated by the class's calculate_key method applied to the target instance method. - ``deletion_methods``: Sequence of callable objects taking single argument, a reference to this object which will be called when *either* the target object or target function is garbage collected (i.e. when this object becomes invalid). These are specified as the on_delete parameters of safe_ref calls. - ``weak_self``: Weak reference to the target object. - ``weak_func``: Weak reference to the target function. Class Attributes: - ``_all_instances``: Class attribute pointing to all live BoundMethodWeakref objects indexed by the class's calculate_key(target) method applied to the target objects. This weak value dictionary is used to short-circuit creation so that multiple references to the same (object, function) pair produce the same BoundMethodWeakref instance.
Method | __new__ | Create new instance or return current instance. |
Method | __init__ | Return a weak-reference-like instance for a bound method. |
Class Method | calculate_key | Calculate the reference key for this reference. |
Method | __str__ | Give a friendly representation of the object. |
Method | __nonzero__ | Whether we are still a valid reference. |
Method | __cmp__ | Compare with another reference. |
Method | __call__ | Return a strong reference to the bound method. |
Create new instance or return current instance.
Basically this method of construction allows us to short-circuit creation of references to already- referenced instance methods. The key corresponding to the target is calculated, and if there is already an existing reference, that is returned, with its deletion_methods attribute updated. Otherwise the new instance is created and registered in the table of already-referenced methods.Return a weak-reference-like instance for a bound method. - ``target``: The instance-method target for the weak reference, must have im_self and im_func attributes and be reconstructable via the following, which is true of built-in instance methods:: target.im_func.__get__( target.im_self ) - ``on_delete``: Optional callback which will be called when this weak reference ceases to be valid (i.e. either the object or the function is garbage collected). Should take a single argument, which will be passed a pointer to this object.